A mixer for producing mixed rubber which is a material of a rubber product by mixing a material to be mixed with various additives blended with, for example, raw rubber by rotating a pair of rotors in a chamber is generally known.
In the mixer, the pair of rotors rotates in directions different from each other, whereby the material to be mixed is pushed into a gap between the pair of rotors, and thus mixing is performed.
Here, in the material to be mixed, a degree of plasticity or the like is different according to a difference in material thereof, and therefore, even if the mixer is operated under the same conditions with respect to all the materials to be mixed, there is a case where it is not possible to sufficiently mix the material to be mixed. Therefore, for example, in the invention stated in PTL 1, correction of power consumption in a mixer is performed such that mixing is efficiently performed according to a material of the material to be mixed.